Robotics for transporting containers and objects within an automated analytical instrument and service tool for servicing robotics

ABSTRACT

A robotic arm has a pair of gripper fingers designed to grip a variety of containers, including capped and uncapped test tubes as well as containers having unique gripping means. The fingers each have upper and lower projections separated by a groove, the respective projections facing each other when mounted to grippers on the robotic arm. The projections and groove serve to firmly hold the containers as well as self-align the unique gripping means on initially unaligned containers within the fingers as the fingers close around the containers. The fingers have clearance to avoid contact with caps on capped test tubes. Stops are provided at the top of each finger to engage one another and prevent fully closed fingers from deforming. The robotic arm may be transported along a rail mounted above the instrument and a gripper assembly, having a gripper arm, mounted to the robotic arm may be rotated above the instrument to move the container to various locations within the instrument. Side posts on the instruments have a gap between them that permits the gripper arm to rotate and extend outwards to interface with an adjacent instrument or a lab automation transport line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.09/115,080, filed Jul. 14, 1998.

This application is related to the following U.S. patent applications,having the indicated titles, commonly assigned to the Bayer Corporationof Tarrytown, N.Y. and incorporated by reference herein:

(a) design patent applications for Gripper Finger, Ser. No. 29/090,683,filed concurrently herewith; Sample Tube Rack, Ser. No. 29/090,547,filed Jul. 10, 1998; and Sample Tube Rack, Ser. No. 29/089,359, filedJun. 15, 1998;

(b) utility patent applications for Sample Tube Rack, Ser. No.08/978,715, filed Nov. 26, 1997; Sample Tube Rack, Ser. No. 09/097,790,filed Jun. 15, 1998; Reagent Package, Ser. No. 08/985,759, filed Dec. 5,1997; Diluent Package, Ser. No. 29/088,045, filed May 14, 1998;Automatic Handler for Feeding Containers Into and Out of An AnalyticalInstrument (“Sample Handler”), Ser. No. 09/115,391, filed concurrentlyherewith; Automatic Decapper, Ser. No. 09/115,777, filed concurrentlyherewith; and Cup Handling Subsystem for an Automated Clinical ChemistryAnalyzer System, Ser. No. 09/099,739, filed Jul. 14, 1998.

FIELD OF THE INVENTION

This invention relates to the use of one or more robotic arms in anautomated analytical instrument to transport test tubes and othercontainers or objects between various locations within the instrumentand optionally to and from a transport line system in an automatedlaboratory transport system.

BACKGROUND OF THE INVENTION

Robotics have been incorporated into analytical instruments in variousways. The most common use of robotics in these instruments has been totransport a pipette to aspirate liquid from a test tube. Another use ofrobotics has been to transport a test tube rack within an automatedtesting system, as described in U.S. Pat. No. 5,260,872.

Robotics have also been used to transport test tubes within aninstrument. For example, U.S. Pat. No. 4,835,711 to Hutchins et al.illustrates a robotic arm transporting a test tube to various workstations which are placed in a circle around the robotic arm. Therobotic arm is mounted to a fixed position on the workstation androtates about an axis perpendicular to the surface of the workstation.As illustrated, the test tube appears to be gripped within gripperfingers, the ends of which are curved in the shape of the test tube. Noprovision is made to transport containers other than test tubes.

Another robotic arm for transporting a test tube is shown inInternational Publication No. WO 90/03834. This robotic arm rotates andmay lift or lower the test tube but the robotic arm is not translatablealong any axis. The gripper fingers are only shown and described asgripping a test tube.

U.S. Pat. No. 4,835,707 to Amano et al. describes a robotic arm that ismounted to the central portion of the workstation and articulates in thex, y, and z axes and rotates in the theta direction. The robot may graspa sample tube or one of various circular nozzles on the workstation witha chuck.

International Publication No. WO 93/15407 describes the movement of atest tube with a robotic arm with a “hand” to carry the test tubebetween a mosaic of tesserae of devices and subsidiary devices. Therobotic arm may move along a rail in a first axis and a horizontal armis translatable along second and third axes (vertically andhorizontally) and is pivotable about an axis of rotation. Thisapplication also teaches that more than one similar apparatuses may beadjoined by and cooperate with another by extending the rails supportingthe robots to extend over the adjoining apparatus.

While extending a rail from one apparatus to another similar apparatusis one approach to moving a robotic arm between instruments, thisapproach is not ideal for transporting objects between more than a fewinstruments as the rail along which the robotic arm must move becomessignificantly long. A better alternative is to use a lab automationtransport line to transport test tubes between instruments positionedalong the side of the transport line. One such transport line isdescribed in U.S. Pat. No. 5,623,415 to O'Bryan and assigned toSmithKline Beecham Corporation. In the O'Bryan patent, a genericpick-and-place engine, with a robotic arm and grip, is referenced as themeans for transferring test tubes between the transport line and theinstruments. Alternatively, a pipetting engine may pipette specimens ofsamples from the test tubes in the transport line for use by theinstrument.

SUMMARY OF THE INVENTION

It is an object of this invention to provide one or more robotic armshaving gripper fingers that may grip and transport individual containersof various types, including various types and sizes of test tubes(including tubes to hold samples, calibrators and controls), customizedreagent and diluent packages, dilution cups and pretreatment incubatorcovers, from a first, source location to a second, destination location.For simplicity, unless otherwise specified, the term “container” as usedin this application shall include, but not be limited to, objects andeach of the foregoing specifically enumerated examples of containers.The robotic arm(s) of the present invention may be advantageously usedin a variety of applications, such as a means of transport betweenmodules of a modular automated analytical instrument or between ananalytical instrument and a sample transport line.

It is a further object of this invention to provide an analyticalinstrument that may have at least two robotic arms wherein one of therobotic arms is capable of handling the full workload of the instrumentif the other robotic arm is disabled.

It is a further object of this invention to provide a robotic arm thathas a first attachment for transporting various types of containers froma first location to a second location in an automated analyticalinstrument and an interchangeable second attachment for transporting thecontainers from the instrument to a lab automation system or vice versa.

It is a further object of this invention to provide a service tool,which is used to remove robotic arms easily for replacement and service.

It is a further object of this invention to provide a self-teachingprocess for the robotic arms to account for slight variations in thelocations of areas on the instrument which are addressable.

To achieve these objectives, a robotic arm for an analytical instrumenthas two translational degrees of freedom, a first along the x-axis and asecond along the z-axis, and one rotational degree of freedom in a thetadirection about the z-axis. The robotic arm comprises a platform thatmay move along a rail running above the rear of the instrument anddefining the x-axis, a lead screw assembly coupled to the platform anddefining the z-axis, a gripper arm coupled to the lead screw assembly tomove along the lead screw, grippers mounted to the outer end of thegripper arm, and two gripper fingers. The gripper arm, grippers, andgripper fingers may collectively be referred to as the gripper assembly.The x, z and theta movements are powered by respective servo motors andthe grippers are coupled to electronics mounted above the grippers,including an inertia switch and an encoder. An analytical instrument mayhave at least two of these robotic arms to increase the throughput ofthe instrument and to provide redundancy in the event that one of therobotic arms fail.

In a first aspect of the present invention, each of the gripper fingerson the robotic arm have upper and lower projections separated by agroove. The grooves allows the fingers to grip and transport varioustypes of containers that have flanges that fit within the grooves,including specialized containers, such as reagent and diluent packagesand dilution cups designed for use with the instrument, or othercontainers with flanges. In addition to capturing the flange, the grooveself-aligns a misaligned container as the fingers close around theflange by pushing down on the top of the flange with the bottom of theupper projections and pushing up on the bottom of the flange with thetop of the lower projections. The fingers may use the upper and lowerprojections to grip and transport other containers with cylindricalexterior gripping surfaces, including individual test tubes where thefingers are sufficiently long.

In another aspect of the present invention, the distance to which thefingers separate from one another is limited to a distance smaller thanthe opening of the grippers. This is preferably accomplished with a rodmounted to one of the fingers, passing through an aperture on the otherfinger, and ending in a stop, which prevents the fingers from separatingmore than a desired distance.

In another aspect of the present invention, the robotic arm may have anabsolute encoder either coupled to the gripper assembly, the platform,or preferably a separate absolute encoder for each of the gripperassembly the platform to determine whether the robotic arm is in aposition where it may be safely homed without hitting an obstruction.

In another aspect of the present invention, because it is desirable incertain situations for the reach of the robotic arm not to extend tosome areas of the chassis, the robotic arm may instead reach theselocations by inserting a container into or removing a container from ashuttle on the chassis that moves along the y-axis and provides accessto at least some of those locations to which the robotic arm cannotreach. The shuttle is preferably a rack that may hold multiplecontainers.

In another aspect of the present invention, the analytical instrument isdesigned to be used in conjunction with a laboratory automation system.The instrument has side posts and a gap between the side posts that islarge enough to allow the gripper arm to pivot outside of the instrumentwith a sufficient reach for the fingers to transport test tubes betweenthe transport line of the laboratory automation system and theinstrument.

In another aspect of the invention, the platform of the robotic arm iscoupled to the rail on the instrument with a bearing plate to simplifythe removal of the robotic arm for service or replacement. The serviceor replacement may be further simplified, in yet another aspect of theinvention, with a service tool that is mounted to one side of theinstrument. The robotic arm may be transferred from the rail on theinstrument to a rail extension on the service tool for easier access.

BRIEF DESCRIPTION OF THE DRAWINGS

The inventions and modifications thereof will become better evident fromthe detailed description below in conjunction with the followingfigures, in which like reference characters refer to like elements, andin which:

FIG. 1 is an isometric view of a first embodiment of a single roboticarm of the present invention mounted to a beam, which is positioned overvarious modules of an analytical instrument, and adjacent to a transportsystem of a laboratory automation system;

FIG. 2 is an isometric view of the robotic arm of FIG. 1 mounted to thebeam with the gripper arm fully lowered;

FIG. 3A is an isometric view of the beam including the rail and rackalong which the robotic arm moves in the x-direction;

FIG. 3B is a perspective view of the zonal homing bar;

FIG. 4A is an isometric view of the top of the saddle platform mountedto the rail and coupled to the rack (the remainder of the beam androbotic arm are not shown);

FIG. 4B is an exploded view of the top of the saddle platform separatedfrom the bearing plate;

FIG. 4C is a further exploded view of the saddle platform without thebearing plate;

FIG. 5A is an isometric view of the bottom of the saddle platform andthe theta-motor and z-motor assemblies (the lead screw assembly is notshown);

FIGS. 5B and 5C are exploded views of the bottom of the saddle platformshown in FIG. 5A;

FIG. 5D is a top view of the theta homing plate mounted above the thetaencoder ring;

FIG. 5E is a cross-sectional view along line 5—5 of FIG. 2 of the kitmotor housing surrounding the upper portion of the robotic arm includingthe z-motor;

FIG. 5F is a side view of an incremental encoder that may be used totrack the position of the gripper arm along the z-axis;

FIG. 6A is a perspective view of the robotic arm with the arm in a fullylowered position along the z-axis;

FIG. 6B is a cross-sectional view of the portion of the robotic armshown in FIG. 6A along line 6—6;

FIG. 7 is a perspective view of robotic arm with the gripper arm raisedalong the lead screw assembly;

FIG. 8A is an isometric view of a gripper arm from the left side of thegripper arm;

FIG. 8B is an isometric view of the gripper arm from the right side ofthe gripper arm;

FIG. 8C is a rear view of the gripper fingers;

FIG. 8D is a top view of the encoder plate mounted to the fingers;

FIG. 9 is a perspective view of the robotic arm having a gripper armaccording to a second embodiment of the invention;

FIG. 10 is a rear view of a gripper arm shown in FIG. 8;

FIG. 11A is a perspective view of the robotic arm gripping a test tube;

FIG. 11B is a perspective view of an incubator cover that may be grippedby the robotic arm;

FIG. 11C is a perspective view of a predilution cup, which may begripped by the robotic arm;

FIG. 12 is an isometric view of a reagent package having a grippingblock from which fingers on robotic arm may grip the package;

FIG. 13 is an isometric view of fingers gripping the reagent package ofFIG. 12;

FIG. 14 is a plan view of a representation of a positional ambiguitypresented by a robotic arm that may move in x and theta directions;

FIG. 15 is a top view of theta homing plate;

FIG. 16 is a front view of two robotic arms mounted to a beam;

FIG. 17A is a front view of the service tool for the robotic arm; and

FIG. 17B is a bottom view of the service tool of FIG. 17A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an analytical instrument 10 has a sample handlermodule 20 for feeding test tubes of various sizes and other containersto the instrument 10, and one or more additional modules, at least someof which may be optional. The modules prepare a supplied test tube foranalysis, if necessary, and then perform one or more analyses on thetest tube. Sample handler 20 may include an automatic decapper, asdescribed in the referenced Automatic Decapper application, (not shownin FIG. 1 but which may be located in location 30) for decapping cappedtest tubes and a reagent activator 36 for preparing reagent packages foruse by analytical modules. There may also be a module 31 for processingthe tubes before analysis, including a predilution apparatus for addingreagents and diluents to and incubating samples (as described in thereferenced “Cup Handling Subsystem” application), and an ion selectiveelectrode apparatus for measuring electrolytes in body fluid. There mayalso be one or more analytical modules including a clinical analysismodule 33, and an immunoassay module represented by box 34. Containersthat are transported within the instrument include various types andsizes of capped or uncapped test tubes (including tubes, with or withoutinsert cups, to hold samples, calibrators, and controls), customizedreagent and diluent packages, dilution cups and pretreatment incubatorcovers (which cover the dilution cups in the heated dilution moduleduring the dilution process to confine the heat).

A beam 40 runs above the rear of the instrument 10. (FIG. 2) The lengthof beam 40 will vary depending on the length of the instrument 10, whichmay have a varying number of modules. A robotic arm 100, which reachesover at least a rear area of instrument 10, and which for safety reasonsis preferably not accessible to the operator, is mounted to beam 40 andis designed for picking up and transporting the containers. Robotic arm100 comprises several sections, including saddle platform 101, avertically mounted lead screw assembly 102, a gripper arm 103 coupled tolead screw assembly 102 on one end, and a gripper actuator 104 andgripper fingers 105, including right finger 105 _(R) and let finger 105_(L), mounted to the other end of gripper arm 103 for gripping thecontainers.

Robotic arm 100 has four degrees of freedom of movement above the samplehandler 20 and modules 30-34. First, the entire robotic arm 100 may movelinearly in the x-direction defined by beam 40 along saddle platform101. Second, gripper arm 103 may also move linearly up and down alongthe z-axis defined by lead screw assembly 102. Third, lead screwassembly 102 is rotatable, thereby causing an angular (or theta) motionof gripper arm 103 about the z-axis in a theta direction. Fourth,gripper fingers 105 open and close linearly.

As shown in FIG. 3A, beam 40 comprises a precision plate 110, a beam boxassembly 111 mounted to the bottom rear of precision plate 110, a rack112 mounted to the bottom of precision plate 110 in front of beam boxassembly 111, and a linear sliding rail 113 mounted to the bottom ofprecision plate I 10 in front of rack 112. The length of beam 40, rack112 and rail 113 will depend on the number and size of analyticalmodules in instrument 10.

Rotatable hard stops 120-123 are mounted across the top front of beam40, two near each end of beam 40. Hard stops 120-123 may be rotatedupward and into respective exposed recesses 130-133 on the front of beam40 or may be turned down as shown. Also mounted to the front of beam 40across the top left side of beam 40 is a zonal homing bar (FIGS. 1 and3B). The function of hard stops 120-123 and zonal homing bar 580 will bediscussed in more detail below.

Robotic arm 100 is mounted to beam 40 with one or more bearing blocks.In the preferred embodiment, the bearing blocks may comprise two linearball retained bearing blocks 150, 151 coupled the top of saddle platform101 that are mounted to and linked together by bearing plate 154. (FIGS.4A and 4B) Bearing blocks 150, 151 may be purchased premounted by themanufacturer to rail 113. While rail 113 may vary in length, preferredrails with premounted bearing blocks are manufactured by IKO of Japan asthe LWE series. (For example, for a rail that is 1660 mm long, thepreferred rail with bearing blocks is IKO model number LWESC20C2R1660H.)A tongue 152 on each of bearing blocks 150, 151 slides along tracks 153a, 153 b on the front and back of rail 113. Alternatively, rollerbearings may be used to couple robotic arm 100 to rail 113, instead ofball bearings. In determining the number and type of bearing blocks touse, one must take into account that the bearing block or blocks mustcarry the maximum load of robotic arm 100 loaded with the heaviestcontainer it may carry, and must be able to accelerate and travel at thedesired speeds smoothly while keeping noise to a minimum, minimizingtorque about each of the x, y and z axes to maintain robotic arm 100relative to the predefined locations on instrument 10 which it mustreach, and not wearing excessively. The maximum torque of each ofbearing blocks 150, 151 may be determined from handbooks obtainable fromthe bearing block manufacturer. Saddle platform 101 is removably mountedto bearing plate 154 to easily remove robotic arm 100 at saddle 101 forservice.

Referring to FIGS. 4A and 5B, robotic arm 100 is driven in a linearmotion along the x-axis by an “x-motor” 160 mounted beneath saddleplatform 101. X-motor 160 is preferably a brushless closed-loop servomotor coupled to a gear box and has a built-in incremental encoder totrack the position of robotic arm 100 along rail 113. X-motor 160 may bethe motor manufactured by Parker/Compumotor of Rhonert Park, Calif. asModel No. CM160XE-00438 that has a built-in optical encoder to track theposition of robotic arm 100 and has a gear box with a gear ratio betweenthe motor and gear of 5.5:1. The particular motor 160 is selected toachieve the desired speeds and accelerations, to prevent oscillations ofthe robotic arm and to provide smooth transitions when accelerating anddecelerating to minimize jerk, which may cause samples in open testtubes to spill and may cause excessive noise. A drive shaft 161 onx-motor 160 passes through saddle platform 101 and attaches to a pinion164 above saddle platform 101. Pinion 164 engages against rack 112,thereby driving robotic arm 100 in the x-direction. X-motor 160 ismounted to an adjustable mounting plate 166 (FIG. 5C) and mounting plate166 is mounted to saddle platform 101. Slots 167 on mounting plate 166allow for the minor adjustment of x-motor toward or away from rack 112to accommodate some imprecision in the mounting of rack 112 along beam40. Pinion 164 is held in place with a split hub clamp (not shown).

A “theta motor” 170 to rotate gripper arm 103 in a theta direction ismounted to a mounting plate 176 and mounting plate 176 is then mountedto the top of saddle platform 101. (FIG. 4C). Slots 177 in mountingplate 176 provide for the minor adjustment in the positioning of thetamotor 170. A drive shaft 172 of theta motor 170 passes through a hole179 in the bottom of saddle platform 101 and a pulley 174 is attached atthe end of drive shaft 172. Pulley 174 is indirectly coupled to aplanetary gear 180 mounted underneath saddle platform 101 with asynchronous timing drive belt 181 having teeth. (FIGS. 5A-5C) Drive belt181 is tightened in place with idler point 182 attached to a mountingpin 183 on the bottom of saddle platform 101 that increases the lengthof drive belt 181 which contacts pinion 174 and planetary gear 180 andprovides for the proper tensioning of drive belt 181. Planetary gear 180is held in place with a thrust plate 184. A preferred theta motor 170may be identical to x-motor 160. The drive ratio between planetary gear180 and pulley 174 for theta motor 170 should preferably be 10:1.

The various components mounted between saddle platform 101 and thrustplate 184 are shown in an exploded view in FIG. 5C. An aperture 190 insaddle platform 101 extends downward from saddle platform I 0 1 throughthe bottom of a circular projection 191 formed at the bottom of saddleplatform 101. An absolute two-bit encoder is provided to create zonesalong theta over which it is safe to home as described below. Theabsolute encoder comprises an encoder ring 211 and two optical vane-typesensors 212, 213. Sensor 213 is mounted farther from the center ofencoder ring 211 than sensor 212. The operation of encoder 210 will bedescribed below. Homing in the theta direction is achieved by a homingplate 214 mounted to encoder ring 211, and planetary gear 180 and homingstop pin 217 extending from saddle platform 101 (FIG. 5D). Homing stoppin 217 on the bottom of saddle platform 101 is positioned within anarcuate slot 216 on homing plate 214. Kit motor housing 220 (FIGS. 5Aand 5B) is mounted to the bottom of planetary gear 180, and the top oflead screw bracket 190 is mounted to the outside of housing 220 at point222 on connector 221. (FIG. 5A)

The activation of theta-motor 170 causes the rotation of planetary gear180 and the theta rotation of robotic arm 100. The theta range ofmovement is limited to less than 360 degrees to avoid hitting a possibleback wall on instrument 10. In the illustrated embodiment, the thetarange of movement is limited by homing stop pin 217 inserted in slot 216which extends around only a portion of homing plate 214.

A “z-motor” 240 raises and lowers gripper arm 103 in the z-direction.Z-motor 240 is preferably a brushless closed-loop servo motor assembledbelow saddle platform 101 from a kit motor. The kit motor comprises arotor 241 that is press fit onto a lead screw 250 and a stator 242 thatis press fit to the inside of kit motor housing 220. (FIG. 5E) Onesuitable kit motor for z-motor 240 is manufactured by MFM Model No.K032. An incremental encoder is also provided to track the position ofrobotic arm in the z directions.

Motors 160, 170 and 240 are conventionally powered and controlled bystandard power distribution and servo control cards mounted in a tray(not shown) on instrument 10 and connected to a wiring harness 300 witha laminated, flexible cable 260 (FIG. 2). The servo circuitry permitsthe detection of obstructions to the motion of robotic arm 100 andposition loss. If an error is detected, a recovery procedure to attempthoming of robotic arm 100 (in the particular dimension in which it wasdetected) that caused the error is initiated to resume normal operation.If the circuitry is unable to recover, robotic arm 100 stops moving andthe user is alerted.

Cable 260 is preferably cambered for smoother, controlled movement ofthe cable as robotic arm 100 moves along rail 113. As shown in FIG. 2,wiring harness 300 is connected to cable 260 above an L-shaped plate 255mounted to saddle platform 101 and overhanging beam 40.

Controlling the operation of instrument 10 are multiple controllers.Preferably, one controller, such as a controller from Galil ofCalifornia, Model No. DMC1503 or a similar controller, is used for eachrobotic arm (i.e., both robotic arm 100 and robotic arm 200 referencedbelow) to store parameters and profiles for controlling the robotics. Aseparate master microcontroller for sample handler 20, such as amicrocontroller based on the Intel 386EX processor, communicates withcontrollers for the other modules 31, 33 and 34 via a standard CAN busand performs various mathematical calculations that may be required tooperate the robotics.

Mounted above the z-motor 240 and within kit motor housing 220 is abearing 270 through which lead screw 250 passes and mounted abovebearing 270 is an optical encoder 280 with commutation tracks formeasuring the rotation of z-motor 240 and thereby tracking the movementof gripper arm 103 along the z-axis. The top of lead screw 250terminates within the center of optical encoder 280.

One suitable optical encoder 280 for z-motor 240 is the RCM15Commutation 1.5″ encoder manufactured by Renco of Goleta, Calif. Opticalencoder 280 has commutation tracks in quadrature (i.e., the commutatorhas four zones demarcated by two rows of commutation tracks around thecircumference of a glass disk which rotates within optical encoder.)Glass disk 281 is fit onto lead screw 250 and is driven by the rotationof lead screw 250. The body 282 of optical encoder 280 is mounted withinkit motor housing 220.

A space 290 is left in housing above optical encoder 280 for wiring fromwiring harness 300 which passes through an aperture 190 in the bottom ofsaddle platform 101 and into space 290. Wiring harness 300 passes outthe bottom of kit motor housing 220 at 310 (FIG. 4C and 5B) and entersthe top of gripper arm 103 through an aperture 320. (FIG. 6A) Wiringharness 300 then passes within gripper arm 103 to gripper actuator 104.In this manner, wiring harness 300 does not interfere with the movementof robotic arm 100.

Gripper arm 103 extends the reach of fingers 105 to reach all areas ofinstrument 10 to and from which containers are to be moved by roboticarm 100. In the preferred embodiment, the reach does not extend to thefront area of the instrument. Containers are fed into and out of therobot-accessible areas of sample handler 20 by the sample handler itselfand containers are transported toward the front of the analyticalmodules, such as modules 33, 34 on a rack 37 on shuttle 38.

Gripper arm 103 may be sloped downward from its proximal to distal endsto reduce the required length of lead screw assembly 102 and therebyminimize interference posed by possible components or other obstructionssituated under lead screw assembly 102.

FIG. 6B illustrates the coupling of lead screw assembly 102 to afully-lowered gripper arm 103. A zero lash plastic slip nut 330 that isthreaded on the inside is placed onto lead screw 250. A brasscylindrical insert 340 that is threaded on both its interior andexterior is threaded on its interior onto slip nut 330 and glued to slipnut 330. Insert 340 is inserted through a hole 350 in the bottom ofgripper arm 103 and a split collar 360 is tightened to the bottom ofinsert 340 to lock gripper arm 103 to insert 340.

The bottom of lead screw 250 sits in a bearing 370. Bearing 370 is heldin place with an adjustment nut 380 tightened to the bottom of leadscrew bracket 190. A circular wave spring 390 is inserted betweenadjustment nut 380 and lead screw bracket 190 to accommodate thermalexpansion in lead screw 250. A void 400 is left between the bottom oflead screw 250 and adjustment nut 380 to permit the rotation of leadscrew 250.

Threading on lead screw 250 preferably moves gripper arm 103 12½ mm perrevolution of lead screw 250 to provide a smooth motion and lessen theeffects of the inertia of a load on the motion of gripper arm 103. Thethreading also provides precise control over the vertical movement ofgripper arm 103.

To raise gripper arm 103, z-motor 240 is activated in a first directioncausing lead screw 250 to rotate. Two pillow blocks 410, 411 at one endof gripper arm 103 slide along a rail 420 (FIG. 7) mounted to lead screwbracket 190. If gripper arm 103 is fully raised, the top of upper pillowblock 410 hits a hard stop 430 along rail 420 and a pin 440 thatfunctions as a z-axis homing flag on the side of gripper arm 103 engageswithin a plug-shaped, through-beam infrared sensor 450. This interruptsan infrared light beam, which is transmitted out of a transmitter on oneside 451 of sensor 450 and otherwise received on the other side 452 ofsensor 450 (FIG. 3B).

To lower gripper arm 103, z-motor 240 is activated in the oppositedirection. A hard stop 460 is mounted to the bottom of lead screwbracket 190 (FIG. 6B). An insert 470 is press fit into the bottom ofgripper arm 103 adjacent rail 113 to reference (i.e., contact) hard stop460 if gripper arm 103 is fully lowered along lead screw bracket 190.

A vertical mount area 480 is provided on the outer end of gripper arm103 for mounting gripper actuator (“grippers”) 104, which is aconventional parallel grippers. (FIGS. 8A and 8B) The back of grippers104 mount to the front of vertical mount 480. Grippers 104 are designedto be easily removable for replacement or service by the removal of fourthumb screws 481. Grippers 104 are a horizontal grippers, as opposed toa vertical grippers, to provide space on top of grippers 104 formounting a printed circuit board 500 with various electronicscomponents. One suitable grippers is model RPL-3 manufactured byRobohand Inc. of Monroe, Conn. Fingers 105 are mounted to the front ofgrippers 104.

Printed circuit board 500 is mounted to posts 505 that are mounted tothe top of grippers 104 and various electronic components are mounted tothe top of printed circuit board 500, including an inertia switch 510,an optical vane-type sensor 530, such as an infrared through-beamsensor, and an incremental encoder 540. Inertia switch 510 immediatelydetects a collision between fingers 105 or grippers 104 and some otherobject and to immediately stop the movement of grippers 104. Sensor 530detects when grippers 104 are fully closed when infrared beam on sensor530 is interrupted by a U-shaped flag 531 that is mounted to the top ofone of fingers 105, the right finger in the illustrated embodiment.Printed circuit board 500 processes signals received from inertia switch510, sensor 530 and encoder 540 and communicates with the controller forrobotic arm 100.

Encoder 540 tracks the opening and closing of grippers 104 and therebydetermines the width of the container which is gripped by grippers 104by determining the size to which gripper 104 remains after gripping acontainer. Encoder 540, which may comprise an encoder manufactured byHewlett-Packard as Model HEDS 9100, preferably has two infrared beamsspaced apart from one another that both counts the number of tracks on aplate 541 (FIG. 8D), mounted to the top of fingers 105, which passessideways through encoder 104 as grippers 104 open and close. Plate 541is transparent except for a pattern of parallel black lines spaced fromeach other by a width equal to the width of a line equidistantly.Infrared beams on encoder 104 are spaced apart from each other out ofphase by 90° to generate identical signals 90° out of phase and toincrease the precision of the measurements to half the width of a line.Whether grippers 104 are opening or closing may be determined from theshape of the signal generated.

In an alternative embodiment, shown in FIG. 9 without a printed circuitboard or other electronics mounted to gripper 104′, vertical grippers104′ are mounted to a horizontally-positioned mount area on a slightlydifferent gripper arm 103′. The top of a grippers 104′ mounts to themount area on gripper arm 103′ and fingers 105′ mount to the bottom ofgrippers 104′. However, this embodiment may not leave enough space tomount the electronics thereon.

Grippers 104 are pneumatically operated with air ports (not shown) toinject air into a double action air cylinder in grippers. Pressureapplied on one side of the cylinder opens grippers 104 along withfingers 105 and pressure applied on the other side of the cylindercloses grippers 104 and fingers 105. Grippers 104 maintain a closedposition when not in the process of picking up or releasing a containerso as not to drop the container if air pressure is lost while holdingthe container.

Valves and air tubes (not shown) are located as close as possible torobotic arm 100 to be able to respond to the activation of grippers 104as quickly as possible. When otherwise unconstrained, grippers 104 mayopen more than is desirable and than the manufacturer's specificationsfor the grippers such that the outer side of fingers 105 might hit anadjacent container or obstruction. Therefore, referring to FIGS. 8B and11A, a means for limiting the separation of fingers 105 independently ofgrippers 104 is incorporated into fingers 105. The limiting meansconsists of a rod 553, mounted to the inner face of one of the fingers105, such as left finger 105 _(L), that passes through a correspondinghole 554 on the inner face of right finger 105 _(R). Rod 553 has a stop556 at the end that is larger than hole 554 and limits the opening offingers 105. When fingers 105 are closed, stop 556 extends into a hole555 on the outer face of finger 105 _(R) that provides clearance forstop 556.

The gripping force of grippers 104 should preferably be limited, such asto a range of 25-30 psi, to minimize the deflection of fingers 105 andlimited so that it does not exceed 50% of the force necessary to crushthe weakest test tube that will be used in instrument 10.

Robotic arm 100 is designed to transport the various containersreferenced above. Fingers 105 must therefore be versatile and strongenough to resist bending by the heaviest load placed on robotic arm 100.Fingers also must be compact enough to avoid hitting obstructions whilemoving containers into and out of areas with tight clearances. Forexample, reagent packages as shown in FIGS. 12 and 13 (such as thepackage described in application Ser. No. 08/985,759) may be insertedthrough an opening 33 a in a cover 33 b on top of clinical analysismodule 33 and into a carousel (not shown) under cover 33 b. Opening 33 amay be only several millimeters wider than the reagent package andfingers 105 must clear opening and have some clearance to insert thereagent package into the carousel. As another example, fingers 105 mustbe able to insert a diluent package, which contains diluent (applicationSer. No. 29/088,045) and is less than half the size of the reagentpackage through opening 31 a in a cover 31 b on module 31, which issmaller than opening 33 a, and into a particular position on anothercarousel (not shown) on module 31. Fingers 105 must also be long enoughso that grippers 104 never descends below any cover on an analyticalmodule where environmental conditions could damage it.

Each of the two fingers 105 are almost identical. Fingers 105 are shapedas shown in FIG. 10 with a pentagonal upper portion 105 _(U) and anarrower lower portion 105 _(B) extending vertically downward. The widertop surface of fingers 105 _(U) provides more stability to fingers whilethe much narrower lower section 105 _(B) allow fingers 105 to movewithin tight spaces. When grippers 104 are opened, the top of upperportion 105 _(U) opens outward over the bottom surface of grippers 104to a width such that the outermost edge 105 _(out) of each finger 105when grippers 104 are fully open does not extend beyond the sides ofgrippers 104.

Referring to FIG. 8C, fingers 105 mount to grippers 104 at grooves 582_(R) and 582 _(L). To keep fingers 105 as narrow as possible to fit intoan area with little room to maneuver, the thickness of fingers 105 isreduced in a top portion 584 and at point 585 the fingers 104 widen sothat when fingers 105 are mounted to grippers 104 the lower portion offingers 105 below point 585 wraps below grippers 104.

To grip the various containers used with instrument 10, two projections550, 551 extend inward from fingers 105 with a groove or channel 552left between the projections. Upper and lower projections 550, 551 areflat on top and bottom and are contoured identically on their innermostsides to have central sections 550 _(C), 551 _(C) which may be curvedand front and back sections 550 _(F), 551 _(F) and 550 _(B), 551 _(B),respectively, which have a straight edge and are angled from one anotherat approximately 120° (the zero reference point of the angle being atthe center of center sections 550 _(C), 551 _(C)). The central sections550 _(C), 551 _(C) are preferably curved at a radius of 3 mm to bettergrip front and rear walls on the gripping block 560 on reagent anddiluent packages described below. The angle between front sections 550_(F), 551 _(F) and back sections 550 _(B), 551 _(B) is selected so thatfingers 105 do not break a test tube when they close around a test tube,which might otherwise occur if the angle between front and back sections550 _(F) and 550 _(B) were less than 120°. Upper and lower projections550, 551 extend an additional approximately 4 mm inwards beyond the 1 mmthickness of the lower portion 105 _(L) of fingers 105. The inner-facingside 105 _(IN) of each of fingers 105 is curved. (FIG. 8) The contour ofside 105 _(IN) and its setback from upper and lower projections 550, 551allows the secure gripping of a test tube while leaving clearance for acap or other closure on a test tube so that the cap or closure does notcontact side 105 _(IN), which could cause the cap or closure to stick tofingers 105 and interfere with the release of the test tube in itsdestination location. The 4 mm difference in diameter between upper andlower projections 550, 551 and side 105 _(IN) is thought to besufficient for caps on most currently-manufactured test tubes that maybe used with instrument 10. However, if caps on various test tubes docontact side 105 _(IN), the difference in diameter between upper andlower projections 550, 551 and side 105 _(IN) may be enlarged.

A beveled edge 535 between upper projection 551 and side 105 _(IN)accommodates caps or closures on short test tubes, such as 75 mm testtubes, which the robotic arm 100 picks up with the lower edge ofscrew-on caps positioned directly above upper projection 551 when a testtube is gripped so the caps preferably do not touch upper projection551. Another beveled edge 537 at the bottom outer edge of fingers 105prevents the fingers 105 from breaking a first test tube if fingers 105knock into that first test tube while picking up a second test tubeadjacent the first test tube.

The height and width of lower projection 550 is also selected to be ableto grip a predilution cup 564 described in the Cup Handling Systemapplication and further described below, and the height and width ofupper projection 551 is selected to be equal to the width of lowerprojection 550. In a preferred embodiment, for reasons explained below,the height of upper and lower projection 551, 550 are respectively,approximately 2 mm and 4 mm. Groove 552, separating upper and lowerprojections 550, 551, is approximately 4 mm high.

When grippers 104 are opened, rod 553 limits the opening of fingers 105so that the exterior sides of fingers 105 separate from each otherapproximately 30 mm, as shown in FIG. 10. Because of the approximately 5mm thickness of lower and upper projection 550, 551, the maximumdiameter of test tubes, incubator covers or other round containers thatmay be gripped by fingers 105 is approximately 20 mm. Due to slightvariation in the length of projections 550, 551, the maximum diametermay be as large as 20.5 mm.

For non-round containers or round containers larger than 20 mm indiameter, a gripping block or other gripping means, preferably includinga flange, must be provided on the containers for robotic arm 100 to liftthem. One particular gripping block 560 may be provided on the top of areagent package, which contains reagents used by instrument 10. Thisparticular reagent package is described in more detail in applicationSer. No. 08/985,759 (which refers to gripping block 560 as “pivot block110”). Gripping block 560 has a front wall 563 and a back wall (notshown but shaped like front wall 563) which is curved to fit within thecontour of fingers 105 and two curved flanges, front flange 561 and rearflange 562, which may follow the same curvature as the front and backwalls. Where the maximum diameter between opposing upper and lowerprojections 550, 551 on left and right fingers 105 _(L) and 105 _(R) isapproximately 20 mm, front and rear flanges 561, 562 must be separatedfrom one another by a diameter of less than 20 mm in order to fitbetween fingers 105. The recesses and contours of the side walls ofgripping means 560 as well as other details of the illustrated reagentpackage are not significant for the purposes of the present application.However, it is important that no elements adjacent the gripping means560 interfere with movement of fingers 105 around flanges 561, 562. Asimilar gripping means may be used on other containers, such as thediluent packages.

Groove 552 serves to properly align an otherwise misaligned container atthe time the container is retrieved. If a reagent package or othercontainer with gripping block 560 or a similar means for gripping thecontainer is not seated at its pick up location completely verticallywhen robotic arm 100 arrives to pick it up, projections 550, 551 andgroove 552 help align the reagent package or other container as fingers105 close around gripping block 560 by catching flanges 561, 562 ofgripping block 560 in groove 552. The top of the flange that is raisedtoo high hits the bottom of projection 551 and is pushed downward whilethe bottom of the other flange that is too low is pushed upward by thetop of lower projection 550. Groove 552 between projections 550, 551 issized to grasp the top flanges 561, 562 on opposite sides of grippingblock 560, while providing some additional space allowance forrealignment of the flanges and to prevent flanges 561, 562 from gettingstuck in groove. Where flanges 561, 562 are approximately 1 mm thick,the 4 mm height of the groove provides the additional space allowancerequired for realignment. Sufficient clearance, at least approximately 7mm, is left on gripping block 560 below flanges 561, 562 for the 4 mmheight of lower projection 550 to grip gripping block 560 while alsoleaving space for realignment.

Stops 570 at the top front of fingers 105 face inward with fingers 105installed on grippers 104. The stops contact each other when grippers104 are closed to counteract the forces propagated through fingers 105by the closing of grippers 104 and the resulting contact of upper andlower projections 550, 551 at the bottom of fingers 105, which otherwisecause fingers 105 to bend. Stops 570 extend inward approximately 4 mmwhich is the width of lower projection 550.

Other containers that may be gripped by fingers 105 include an incubatorcover 557 used by instrument 10 (FIG. 11B) and the dilution cup 564(FIG. 11C). Incubator cover 557 has a cylindrical gripping section 558by which it is gripped. Cup 564 has a cylindrical upper portion 565 thatincludes a bottom flange 566, a top flange 567 and a groove 568 betweenflanges 566 and 567. Lower projection 550 is inserted within groove 568and top flange 567 of cup 564 fits within groove 562 of fingers 105. Theheight of top flange 567 is sized to leave clearance for the uppersurface of top flange 567 to self-align cup 564 during pickup.

Gripper arm 103 and fingers 105 are designed to be as lightweight aspossible by construction with relatively lightweight materials and theuse of various features that lighten gripper arm 103 and fingers 105.Therefore, gripper arm 103 preferably has apertures 575 on the sides ofgripper arm 103 near lead screw 250. For the same reason, an opening 580is preferably left within each of fingers 105 to lighten the weight offingers 105.

As robotic arm 100 is designed to carry, among other things, open testtubes, movements of robotic arm 100 should prevent the jerking of testtubes or other movements which may cause the spilling of samples fromopen test tubes. Of further concern, movements of robotic arm 100 shouldnot disturb samples, which may be incubated in one of modules ininstrument 10. Therefore, the acceleration of robotic arm 100 in thex-direction along rail 113 when carrying a test tube should preferablynot exceed 0.3 g to avoid spillage when carrying an open container suchas a test tube. The acceleration may be increased to as much as 0.5 g ifspillage is not found. When robotic arm 100 transports closedcontainers, including reagent packs, it may accelerate faster. Thisacceleration and deceleration should follow an S-curve-shapedacceleration profile to prevent jerk in robotic arm 100 from propagatingto modules 20, 30-34 in instrument 10. When robotic arm 100 is notcarrying a test tube it may accelerate faster, possibly as high as 1.5g. Vertical up and down movements or gripper arm 103 along rail 420 mayaccelerate up to 1 g. Slew speeds and acceleration profiles for motors160, 170 and 240 must also keep audible noise to a minimum.

Because robotic arm 100 transports containers between specific positionson instrument 10, it must track precisely where it is located. Moreover,in a typical analytical instrument with which robotic arm 100 may beused, there are likely to be areas, such as where other components ofinstrument 10 or beams or walls of the instrument are located, wherecertain movements of robotic arm 100 may be limited. Therefore, homingmechanisms are provided for each of the x-motor 160, theta-motor 170 andz-motor 240 to properly position robotic arm 100 to a known locationafter it is powered up or if robotic arm 100 collides with anotherobject before resuming operation.

Robotic arm 100 may always be homed along the z-axis without any concernof hitting an obstruction because z-axis homing requires only thatgripper arm 103 be fully raised. However, due to the layout of thecomponents on various modules in instrument 10, robotic arm 100 cannotbe homed in the x and theta directions in every location alonginstrument 10 as robotic arm 100 may hit an obstruction if it were homedin certain areas. In particular, homing in the theta direction requiresa large rotation of gripper arm 103 in the theta direction, which onhoming plate 214 is approximately 270°. The layout of instrument 10 inthe configuration shown in FIG. 1, creates some spaces where robotic arm100 cannot be fully rotated over 270° in the theta direction, and otherspaces where robotic arm 100 may be homed in the theta direction.

The first step in the homing process is to home gripper arm 103 alongthe z-axis. Typically, this simply entails raising gripper arm 103 fromwhatever position it is previously in along the z-axis and gripper arm103 is detected to be in a home position when pin 440 on gripper arm 103passes through an infrared beam in through-beam sensor 450. Sensor 450,however, uses “fine edge” detection, meaning that it only detects thefront edge of an object moving upward through the bottom edge of theinfrared beam so if gripper arm 103 is already fully raised at the startof the homing process it is not detected. Thus, when gripper arm 103 isfully raised before homing begins, gripper arm 103 is lowered slightlybeneath sensor 450 and is then returned to its original fully-raisedposition. (FIG. 6).

The homing mechanism next determines if it can be homed in the x andtheta directions. The primary concern in homing in the x-direction isthat robotic arm 100 be able to travel the full length of rail 113without gripper arm 103 hitting an obstruction, including a side wall ofinstrument 10. The primary concern in homing in the theta direction isthat robotic arm 100 not hit an obstruction as it pivots about leadscrew 250.

An absolute two-bit encoder comprising encoder ring 211 and sensors 212,213 adjacent encoder ring 211 provide the information required todetermine if it is safe for robotic arm 100 to home in the x direction.Encoder ring 211 defines four sectors 1-4 (FIG. 15). The size of thesectors may vary but are selected so that movement is permitted in thosesectors in which gripper 103 will not hit an obstruction when roboticarm 100 is moved in the x-direction along rail 113. These sectors willgenerally be confined to areas under beam 40. Thus, in the illustratedexample, sector 1 covers an arc over the left side of the rear ofinstrument 10 under beam 40, sector 2 covers an arc which would positionarm above components of the various modules where there areobstructions, sector 3 covers an arc over the right side of the rear ofinstrument 10 under beam 40, and sector 4 covers an arc where gripperarm 103 would hit a back wall of instrument 10. If robotic arm 100 is tobe homed in the x-direction by moving the left along rail 113, gripperarm 103 must face to the right of instrument 10 with gripper arm 103confined to a position in sector 3. Similarly, if robotic arm 100 is tobe homed in the x-direction by moving the right along rail 113, gripperarm 103 must face to the left of instrument 10 with gripper arm 103confined to a position in sector 1. Thus, before x homing is performed,instrument 10 determines what sector gripper arm 103 is in and, with anexception to be described below, moves it to either sector 1 or 3depending on the direction in which robotic arm is homed. (In a singlerobot arm system, the closest side of instrument 10 may be selected forhoming to home as quickly as possible. In the dual robotic arm systemdescribed below, the left arm would home to the left and the right armwould home to the right.)

The robotic controller determines which sector gripper arm is in byreading the status of sensors 212, 213 and causes gripper arm 103 torotate into homing sector 1 or 3, if it is not there already. Dependingon the theta position of robotic arm 100, the perimeter of encoder ring211 blocks the infrared beam in neither of sensors 212, 213 when thatsector is adjacent sensors so both sensors are ON in sector 4, onlyouter sensor 213 is ON and inner sensor 212 is OFF when sector 3 passesadjacent sensors 212, 213, both sensors are OFF in sector 2 when sector2 is adjacent sensors 212, 213, and inner sensor 212 is ON while outersensor 213 is OFF when sector 1 is adjacent sensors 212, 213. Theabsolute encoder thereby knows what sector the robotic arm is in.

Robotic controller must also insure that gripper arm 103 is in a safearea along the x-axis for the rotation of gripper arm 103 over thetainto sectors 1 and 3 before homing along the x-axis is performed. Therequired determination is made with another absolute two-bit encodercomprising a zonal encoder bar 580 mounted in front of a portion of beam40 (FIGS. 2 and 3B) and two optical vane-type sensors 590, 591 (FIG. 4B)mounted to a sensor mount 593 on the top of saddle platform 101. Sensormount 593 has two tiers 595, with tier 596 elevated above tier 595 toposition sensor 590 higher than sensor 591. The absolute two-bit encoderdemarcates three zones along the x-axis, zones 1-3 (FIG. 3B). It is safeto move gripper arm 103 in the theta direction with the pivot point ofgripper arm 103 (which is around lead screw 250) anywhere in the middlezone 2 and unsafe to move gripper arm 103 in the theta directions inzones 1 and 3 because of obstructions.

Zonal encoder bar 580 extends lengthwise across only a portion of beam40, viz. zones 1 and 2 to minimize the length of bar 580. It isunnecessary for bar 580 to extend to zone 1 and 4. The bottom of zonalencoder bar 580 extends below the front of beam 40 a sufficient distanceto pass through both sensors 590, 591 as robotic arm 100 moves in thex-direction. An elongated opening 598 is left in the zonal encoder for580 toward the bottom of zonal encoder bar 580 across the length of zone2 and is covered with a transparent plastic. When robotic arm 100 is inzone 1, both sensors 590, 591 are OFF because they are blocked by bar580. When robotic arm 100 is in zone 2, lower sensor 591 passes acrossopening 598 and is ON while upper sensor 590 is blocked and is OFF. Bar580 ends at the edge of zone 3 so that when robotic arm 100 is in zone3, both lower and upper sensors 590, 591 are ON.

The precise coding of the sectors and zones defined by encoder ring 211and zonal encoder bar 580 in combination with the sensors, i.e., whichsensors must be ON or OFF to indicate a particular sector or zone, isgenerally unimportant as long as robotic controller has a particularcode associated with each sector or zone. However, because thepositioning of robotic arm 100 is critical to successful homing, thecoding scheme should be a gray coding scheme in which the movement fromone sector into an adjacent sector does not cause both bits for bothsensors 212, 213 along theta to change. There is a similar restrictionfor sensors 590, 591 along the x-axis. Otherwise, a simultaneous changein both sensors would create a brief moment when both sensors in eitherthe theta or x directions are neither ON nor OFF and could lead to aninstability.

If robotic arm 100 is in zone 2 where theta movement is permitted,gripper arm 103 is rotated to sectors 1 or 3 and then x homing may beperformed. X homing is also permitted if gripper arm 103 is already insectors 1 or 3 prior to homing. If, however, robotic arm 100 is in oneof zones 1 or 3 and gripper arm 103 is not in sectors 1 or 3 prior tohoming, robotic controller is unable to home robotic arm 100 withoutmanual intervention. This latter condition should not occur duringnormal operation of instrument 10 unless an operator has previouslyimproperly manually moved robotic arm 100 into such a space where it isimpossible to automatically home.

As described above, the theta homing mechanism also includes homingplate 214 and pin 217 (FIG. 5C).

If the absolute two bit encoders for theta and the x-axis determine thatit is safe for robotic arm 100 to be homed, robotic arm 100 is homedalong the x-axis by moved robotic arm 100 to the left or right until itcontacts a preselected hard stop on beam 40. After robotic arm 100 hasbeen homed against a hard stop, an incremental encoder built intox-motor 160 tracks the precise position of robotic arm 100 along thex-axis. Robotic arm 100 is then moved from the hard stop position tozone 2 for theta homing. To home as rapidly as possible, robotic arm 100need only be moved to the edge of zone 2 closest to the hard stopagainst which robotic arm 100 was homed or slightly inward therefrominto zone 2. Robotic arm 100 is now homed in the theta direction byrotating robotic arm 100 in a clockwise or counterclockwise directionuntil robotic arm 100 no longer rotates because pin 216 in track ofhoming plate 214 prevents further movement. An incremental encoder builtinto theta motor 170 tracks any further rotation of robotic arm 100about theta.

Grippers 104 are maintained in their closed position when not opened togrip a container and are not homed as part of the homing of robotic arm100. If fingers 105 are holding a container at the time that power isturned off, robotic controller will be aware of this because sensor 530on fingers 105 is ON and the operator will be alerted to remove thecontainer.

An uninterrupted power supply (“UPS”) is preferably attached toinstrument 10 to allow for an orderly shut down of instrument 10,including the saving of various information and the transport of acontainer already carried by robotic arm 100 to its destination.

Before containers are input into instrument 10, the user identifies theparticular container to instrument 10 with a bar code placed on thecontainer and other significant information, such as, where thecontainer is a test tube, what tests are to be performed on the samplein the test tube, or, where the container contains reagent or diluent,what reagent or diluent is in the container. The user may also enterinformation that identifies the height of the test tube or othercontainer or the instrument itself may measure the height of the testtube or other container. Using this information, the robotic arm may berequested to transport a particular container, such as when ananalytical module is ready to perform a test on a test tube or hascompleted performing the test, or when an additional reagent package isneeded or is ready for disposal. The user need not enter informationregarding the diameter of a test tube as that information is determinedby how far grippers 104 close during the gripping process.

Software for instrument 10 is programmed into the sample handlermicrocontroller to provide the instructions for the order of priority inwhich containers will be moved. The particular programming will varydepending upon the attached modules and user preference. Also programmedinto the software are the instrument-specific x-y coordinates wherecontainers may be located for pickup or should be dropped off.

The software converts x-y coordinates into x and theta coordinates formoving robotic arm 100. A positional ambiguity is presented by thismapping over x, y coordinates into x and theta coordinates because therobotic arm 100 may approach some x-y coordinates from either an acuteor obtuse theta angle such that saddle platform is in one of twopossible positions along the x-axis. This problem is represented in FIG.14. This ambiguity is simply resolvable by approaching the desired x-ycoordinate from whichever angle enables the x-y coordinate to be reachedas quickly as possible. In other areas, such as the leftmost andrightmost ends of instrument 10, there is no positional ambiguity as aspecific x-y coordinate is only reachable from a single angle theta.

When a module calls for a container, robotic arm 100 moves to thelocation of the requested container by first moving along the x-axis (inthe usual event that fingers 105 cannot reach that x-y location with atheta motion alone). After reaching the required location along thex-axis, theta motor 170 on robotic arm 100 is activated to move fingers105 to the desired x-y position. The built-in incremental encoders inthe motors track movement of x-motor 160 and theta-motor 170. Uponreaching the desired x-y position, the air-activated grippers 104 areopened and gripper arm 103 is lowered by activating z-motor 240. Opticalencoder 280 for z-motor 240 tracks the travel of gripper arm 103 alongz-axis.

The sample handler controller knows the height of each container beforethe robotic arm 100 grips the container and thereby knows the distanceto which gripper arm 103 must be lowered to grip a particular containerand instructs the robotic controller accordingly. To grip a test tubewhose height may vary, robotic controller determines how far to lowergripper arm 103 based on the height, programmed into the roboticcontroller, of two types of customized test tube racks used throughoutinstrument 10. Thus, gripper arm 103 is lowered to position the bottomof fingers 105 approximately 3 mm above the top of a test tube rack inwhich the test tube is located. (The length of test tube extendingbeneath the bottom of fingers 105 is therefore always the same but thelength of the test tube within fingers 105 differs depending on theheight of the gripped test tube.) Grippers 104 then close.

When grippers 104 stop moving toward a closed position due to theresistance of the container to be gripped, encoder 540 will reflect thisby not registering any movement of plate 541 on fingers 105 for 2-3consecutive readings of encoder 540. If sensor 530 does not indicatethat fingers 105 are filly closed, software in the robotic controllerconcludes that a container has been gripped. Linear encoder 540 tracksthe distance over which fingers 105 have closed in order to determinethe width of the test tube or other container and conveys thatinformation to the controller via printed circuit board 500. If sensor530 is activated after fingers 105 have filly closed and a container wassupposed to have been gripped, the controller knows that the pickupoperation was unsuccessful.

The successfully gripped container is then raised by gripper arm 103 byactivating z-motor 240 in the reverse direction, moved to the desiredlocation along the x-y axis, lowered into position, and released byfingers 105.

A second robotic arm 600 may be added to the analytical instrument todivide the workload and improve the throughput of instrument 10. (FIG.16) This second robotic arm 600 is particularly important where a largenumber of modules are included in a single instrument. The secondrobotic arm 600 is identical in construction to and moves along the samerail 113 and rack 112 as the first robotic arm 100. Both robotic arms100, 600 may work in unison. A collision avoidance protocol for avoidingcollisions between robotic arms 100, 600 must be incorporated intosoftware on the sample handler controller.

One possible collision avoidance essentially works as follows (with thetwo robotic arms being referred to generically as robotic arm A androbotic arm B): To avoid collisions between the two robotic arms A andB, the current positions of both robotic arms are tracked. When roboticarm A receives a request to perform an operation, software in the samplehandler controller determines two possible motions of robotic arm Awhich would cause fingers 105 to reach the same point on the x-y plane,which is a “positional ambiguity”, shown in FIG. 14. The first motionwould move robotic arm 100 to a first position on the x-axis and thencause robotic arm A to rotate over a first angle theta. The secondmotion would move robotic arm A to a second position on the x-axis andover a second angle theta to reach the same point. The software thendetermines what movements of robotic arm 100 are needed to get from thepresent position to the new position in either of the two possiblemotion and then estimates whether a requested move of one of the roboticarms, which we will refer to as “A”, will cause that robotic arm A tocollide with the other robotic arm, which we will refer to as “B”. Ifrobotic arm B will not interfere with the movement of robotic arm A ineither the first or second available motions, robotic arm A is moved inthe manner in which fingers 105 which will reach the desired position oninstrument 10 faster. If robotic arm B is not performing a task but onlyone of the two possible motions will not cause a collision between thetwo robotic arms and the motion which is not possible is the faster ofthe two possible motions, robotic arm B is moved out of the way androbotic arm A moves in the manner in which fingers 105 will reach thedesired position faster. But if the faster motion did not require themovement of robotic arm B, robotic arm B would not be moved. If roboticarm B is performing a task and only one of the two possible motions willnot cause a collision between the two robotic arms, robotic arm A ismoved in the motion that does not cause a collision. If robotic arm B isperforming a task and there is no manner in which to avoid a collisionif robotic arm A is moved to the desired destination, robotic arm A isnot moved until robotic arm B finishes its task and moves out of the wayto prevent a collision.

For purposes of homing each of robotic arms 100, 600, robotic arm 100 ishomed in the x-direction by first moving its gripper arm 103 to sector 3and then to the left along the x-axis until it hits hard stop 120 andthereafter moves to zone 2 for theta homing. Robotic arm 100 is thenmoved out of zone 2. Robotic arm 600 is then homed in the x-direction byfirst moving its gripper arm 103 to sector 1 and then to the right alongthe x-axis until it hits the rightmost hard stop 123 and thereaftermoves to zone 2 for theta homing.

In addition to increasing the throughput, the second robotic arm 600also adds redundancy. Should one of robotic arms 100, 600 break down,the remaining working robotic arm may perform all required operations,albeit at a reduced throughput (the actual reduction in the throughputdepending on the tasks which must be performed). The malfunctioningrobotic arm is disabled using the user interface to the software oninstrument 10 and is then manually moved to the side of beam 40 to apark position. Hard stops 121, 122 are utilized to park themalfunctioning robotic arm and to prevent the two robotic arms fromhitting one another. A malfunctioning robotic arm 100 is moved to theleft side of beam 40 against hard stop 120, and hard stop 121, locatedon the opposite side of robotic arm 100 is rotated downward to confinerobotic arm 100 to the park position between hard stops 120 and 121. Amalfunctioning robotic arm 600 is moved to the right side of beam 40against hard stop 123, and hard stop 122, located on the opposite sideof robotic arm 100 is rotated downward to confine robotic arm 100 to thepark position between hard stops 122 and 123.

The park positions of robotic arms 100, 600 may also be used as parkpositions in which routine maintenance may be performed on robotic arms100, 600, including cleaning fingers 105 on the arms.

For easier servicing or replacement or to provide periodic lubrication,robotic arms 100, 600 may be transferred from instrument 10 to a servicetool 700 shown in FIGS. 17A-17B. Service tool 700 comprises a shortextension 710 to beam 40, which may be temporarily inserted into theleft side of beam 40 and a rail 720. Rail 720 is mounted to the bottomof service tool 700 in the same position as rail 113 on beam 40 butthere is no rack on service tool that is equivalent to rack 112. Rail720 extends beyond beam extension 710 and passes under beam 40 tocontact rail 113. In addition, rail 720 is at least as long as thecombined length of the saddle platforms of the two robotic arms 100,600. One or more alignment pins 730 on the right side of rail 720 areinserted into one or more matching holes 735 (FIG. 2) on the left sideof rail 113 to assist in properly aligning rail 720 on service tool 700with rail 113 on beam 40. Alignment pin or pins 730 may be a bullet pin,which is relatively long (on the order of several cm), in order to moreeasily engage the holes on rail 113. Screws 740, 741 or another securingmeans are inserted through holes 745 at the end of beam extension 710and are threaded into corresponding holes on the side of beam 40 tosecure the service tool 700 to beam 40.

To remove robotic arm 100, the service technician disables robotic arm100 using the software, disconnects a connector (not shown) connectingwiring harness 300 on robotic arm 100 to electrical wiring and air lineson the instrument, and rotates upwards whichever of hard stops 120-123is necessary to remove robotic arm 100. After installing service tool700 on the left side of beam 40, the technician manually slides roboticarm 100 alone rail 113 on beam 40 and onto rail 720 on service tool 700.Robotic arm 100 may then be removed by unscrewing the four screwsconnecting saddle platform 101 to bearing plate 154. Or service tool 700with robotic arm 100 on it may be removed. Robotic arm 600 may also besimilarly moved onto service tool 700 after robotic arm 100 is removedeither while robotic arm 100 is on service tool 700 or after robotic arm100 has been removed from service tool 700. Service tool 700 may have ahandle 750 on the top for carrying the service tool 700 but handle 750must be sufficiently short so the top of handle 750 does not hit plate255, which overhangs beam 40 and service tool 700.

In order to save on processing time, the system topology including agrid of all of the potential locations to which a container may be movedis mapped out in software installed in robotic controllers beforeinstrument 10 is first activated.

Instead of inputting test tubes into a sample handler module 20 on theinstrument 10, test tubes may be input into instrument 10 through alaboratory (or “lab”) automation system (not shown), such as the LabCell system from the Bayer Corporation. When operated in this mode,instrument 10 becomes a subsystem in the overall lab automation system.However, rather than pipetting liquid from a test tube when a rack oftest tubes passes adjacent that instrument on a transport system, as ina traditional laboratory automation system, robotic arm 100 is used toremove test tubes from a transport system 800 (FIG. 1) for analysis byinstrument 10 and reinsert test tubes into transport system 800 afterthey have been analyzed. Removing a test tube for various analysesrather than aspirating a small amount from a particular test tube with apipette each time that test tube passes instrument 10 improvesthroughput as instrument 10 does not have wait for the test tube torecirculate through the transport system before aspirating a secondsample for additional analysis.

Preferably, both robotic arms 100, 600 should be used when instrument 10is used as a lab automation subsystem. Robotic arm 100 transports testtubes between a transport system 800 and a shuttle 810 on instrument 10,which may hold several test tubes at a time. A bar code reader andultrasonic liquid level sensor (not shown) are positioned adjacentshuttle 810 to identify the test tubes in shuttle 810 and to determineif the test tubes have caps which must be removed or to read the levelof liquid in the test tubes of those test tubes which do not have caps.After being read by a bar code reader and ultrasonic liquid levelsensor, shuttle 810 then stops in a position where shuttle 810 is helddown as test tubes are removed therefrom by either robotic arm 100 orrobotic arm 600 for transport to various modules within instrument 10other than sample handler 20.

To enable robotic arm 100 to transport test tubes from or into the labautomation system, clearance is provided on the left side of instrument10 for robotic arm 100 to rotate outward with the end of gripper arm 103extending beyond the left side of beam 40 and instrument 10 to reach thelocation of the test tube on transport system 800. To this end, the leftframe of the instrument consists of two vertical posts 812, 813 withclearance between the posts for gripper arm 103 of robotic arm 100 toextend and move in the z and theta directions beyond the left side ofinstrument 10. A removable left side panel (not shown) may be hung overposts 812, 813 when instrument 10 is not interfaced with a labautomation system.

Lab automation systems that cannot be reached with gripper arm 103 mayalso interface with instrument 10 in one of two ways. As onepossibility, a longer beam that extends beyond the leftmost side ofinstrument 10 may be substituted for the ordinary beam 40 to allowrobotic arm 100 to move in the x-direction beyond the left side ofinstrument 10 above transport system 800 on the lab automation system.Alternatively, the gripper arm may be modified to be a two-piece gripperarm with the outer piece, to which grippers 104 mount removable, such asat point 830 (FIG. 11A) and replaceable with a longer second piece thatis longer to reach farther, if necessary. A separate set of grippers 104and fingers 105 may be mounted to the end of the extended second pieceto simplify the substitution. The longer second piece may also be usedon one or both robotic arms 100, 600 where instrument 10 has a module,which requires a robotic arm to have a farther reach.

A serial port on instrument 10 (not shown) for interfacing with the labautomation system is also provided.

One skilled in the art will recognize that modifications and variationscan be made to the above-described embodiment without departing from thespirit and scope of the invention. For example, a robotic arm of thekind described, or with some features removed, may be used on aninterface between a transport line and another instrument, other thanthe one described, to transport containers between the transport lineand the other instrument.

We claim:
 1. A robotic arm comprising a gripper assembly, grippers,gripper fingers mounted to said grippers, an inertia switch coupled tosaid grippers to immediately detect a collision of said gripper assemblywith another object and halt and reverse the grippers in responsethereto.
 2. The robotic arm of claim 1 wherein said grippers furthercomprise means for opening and closing said grippers and an encodercoupled to said grippers to track said opening and closing of saidgripper fingers.